Pneumatic drier of the two-biconical drying chamber type



A. MARK April 20, 1965 PNEUMATIC DRIER OF THE TWO-BICONIGAL DRYING CHAMBER TYPE 2 Sheets-Sheet 1 Original Filed Feb. 16, 1959 \Mmi MMKVENTOR BY -%M&\ W

ATTORNEYS April 20, 1965 A. MARK 3,178,830

PNEUMATIC DRIER OF THE TWO-BICONICAL DRYING CHAMBER TYPE Original Filed Feb. 16, 1959 2 Sheets-Sheet 2 1 II I -30 29 INVENT OR $0M LML United States Patent 3 178,830 PNEUMATIC DRIEROF THE TWO-BICONICAL DRYING CHAMBER TYPE Andr Mark, 54 Cours Lafayette, Lyon, France Original application Feb. 16, 1959, Ser. No. 793,479, new Patent No. 3,078,588. Divided and this application Jan. 2, 1963, Ser. No. 248,958

Claims priority, application France, Feb. 20, 1958, 38,148, Patent 1,192,565 2 Claims. (Cl. 3457) The present application is a division of my prior US. application Ser. No. 793,479, now Patent 3,078,588, and it relates to pneumatic driers comprising one or more vertical drying chambers inserted in a pneumatic drying circuit to receive a gas stream carrying in the suspended state a divided material to be dried, each chamber having a lower axial inlet and an upper axial outlet.

In such driers the drying chamber has been given an upwardly flaring conical shape in order to obtain for the ascending gas stream a progressively decreasing velocity. The heaviest particles, which are generally those which still contain a substantial amount of moisture, have a tendency to float within the chamber, while the lightest and driest ones are carried away through the outlet of the chamber. But in practice the gas velocity is not uniform within the chamber in any horizontal plane. Further the velocity of the gas stream at the inlet of the chamber is not itself quite constant. This has for its result that a quite noticeable proportion of the still moist particles is entrained through the outlet of the drying chamber.

Another object of the present invention is to provide an improved pneumatic drier comprising a substantially vertical drying chamber, wherein the drying power of the drying gas is enhanced in the upper portion of the chamber.

In accordance with the present invention a pneumatic drier comprises a substantially vertical drying chamber of substantially symmetrical shape with respect to a horizontal plane, the said chamber having a lower axial inlet to receive a stream of substantially hot and dry drying gas with the divided material to be dried in suspension therein, an additional gas inlet opening tangentially into the chamber substantially midway of the height thereof, this additional inlet receiving substantially hot and dry drying gas substantially free from suspended particles, and an upper outlet for the drying gas with the treated particles in suspension therein.

It will be appreciated that the tangential inlet imparts to the gas and particles a rotary motion at a relatively high angular speed. The heaviest particles are thus applied against the upper downwardly flaring conical wall of the chamber by centrifugal force and owing to the obliquity of this wall, they tend to roll downwardly against the action of the ascending gas stream, until they are sufliciently dry and light in weight to follow the gas stream rather than the downwardly directed component of centrifugal force. Further the hot and dry gas issuing from the tangential inlet enhances the drying operation in the upper portion of the chamber where the main drying gas stream has already absorbed a noticeable amount of moisture, its drying power being correspondingly lowered.

In the annexed drawings:

FIG. 1 is a vertical section of a first embodiment of this invention, comprising a single drying chamber.

FIG. 2 is a cross-section taken along line IIII of FIG. 1.

ice

FIG. 3 is a vertical section of another embodiment comprising two biconical drying chambers disposed in series.

The pneumatic drier for divided material as illustrated in FIG. 1 comprises a main blower 1 which draws drying gas from a hot air generator 2 and forces this air into a main conduit 3. This conduit 3 is connected through an upwardly directed axial nozzle 4 with the lower end of the conical lower portion 5a of a drying chamber 5. The drying chamber 5 is in turn connected by an exhaust conduit 6 with a conventional centrifugal separator 7. As illustrated, conduit 6 opens axially in the upper end of chamber 5 and it is of course tangent with respect to separator 7. The air outlet of separator 7 is connected with an exhaust blower 8, while the separated solid material is withdrawn by means of a conventional air-lock 9. A branch pipe 10 extends between the main air conduit 3 and a tangential air inlet liia provided in the upper portion of the drying chamber 5, as shown in FIG. 2. The air inlet of the main blower 1 includes an air-lock 12 on which is mounted a feed hopper 13 adapted to re ceive the material to be dried.

The drying chamber 5 comprises an inner axial multiple injector unit formed of a number of successive downwardly flaring frusto-conical elements 14, 15 and 16 with the smaller end of each element engaged into the lower end of the next one and connected with the latter by means of appropriate radial arms. The third element 16 is in one with an upwardly flaring upper element 17 and forms therewith a bi-conical member, and the injector unit rests on lower hooks 18 which support the larger end of the lower element 14, while the upper element 17 of the said unit is maintained by means of a lateral vertical rod 19 which is passed through the upper end of chamber 5 and is adjustably retained by nuts 20.

A sleeve 21 is slidably disposed within the inlet end of the exhaust conduit 6, the lower end of the said sleeve carrying a downwardly flaring member 22. This sleeve 21 is suspended by means of appropriate inner arms to a vertically slidable rod 23 which is passed through the curved wall of conduit 6 and which is itself attached to a vertical rack 24, the latter being in mesh with an adjusting pinion 25.

A grid 26 is disposed in the restricted passage situated between the injector elements 16 and 17, and this grid normally supports balls 27 (which have been illustrated in FIG. 1 as lifted by the ascending air stream).

The operation is as follows:

The main blower 1 forces hot air from the hot air generator 2 through the main conduit 3, the drying chamber 5, the exhaust conduit 6, the centrifugal separator 7 and the exhaust blower S. It may thus be said that conduits 3 and 6 form a single pneumatic drying conduit wherein chamber 5 is inserted. The air jet issuing from nozzle 4 passes axially through the injector elements 14, 15, 16'

and 17 which draw air from the periphery of chamber 5, a substantial portion of the air which leaves element 17 being re-cycled downwardly through the annular space between the peripheral wall of chamber 5 and the axial multiple injector unit.

Air is also injected tangentially into the upper portion of chamber 5 through the tangential inlet 10a. Since the branch conduit 10 opens almost at close to the outlet of the main blower, i.e. in a zone in which the still moist and heavy particles of material pass at a relatively high speed and are not readily deviated laterally in front a I of the opening of the said conduit, this air is hot .and dry and it only contains a very small amount of particles. Consequently the air thus injected into the upper portion of the drying chamber not only causes rotation of the mass of air and particles in suspension within the chamber in a per se known manner, but it enhances the dry: ing power of the airv issuing from the multiple injector and which has already absorbed a substantial amount of moisture from the particles which it conveys.

The balls 27 provided in the injector element 17 are lifted by the ascending air and vibrate above the supporting grid 26' so as to stop and break the heaviest particles entrained. a

The lightest particles, i.e, practically the particles which are substantially dry, are carried away with the moist air which leaves chamber through the adjustable sleeve 21 and are collected in'the centrifugal separator 7. v In the embodiment of FIG. 3 the drier comprises two drying chambers 28 and 29 disposed in vertical succession. These'chambers are of substantially symmetrical bi-conical shape with a short intermediate substantially cylindrical portion, the cylindrical portion of the upper chamber (i.e. the second chamber along the path-of the'air flow) being larger in diameter than thecylindricalportion of the lower chamber 28. The balls 27 are disposed within the upper chamber 29 and their retaining transverse grid 26 is situated at the restricted point of junction of chambers 28. and 29. The branch pipe is divided into two portions 10' and 10" which open respectively into chambers 28 and 29, theirvoutlet being somewhat directed upwardly, as shown. The exhaust blower 8 is. powerful enough for ensuring the air flow' through the apparatus, which dispenses with the main blower 1 of the embodimentof FIG. 1. The drier of FIG. 3 further comprises an additional air pipe 30 which connects the outlet of the exhaust blower 8 with an additional nozzle 31 disposed within nozzle 4 and co-axially with respect to the latter. Divided material to be dried is fed into the lower chamber- 28 from hopper 13a through screw feeder 11, 12a. 7

' When the exhaust blower 8 is invoperatiomthe drying air is drawn through the nozzle 4 underthe combined action of the negative pressure created'by the blower and of the injector effect of the additional inner nozzle 31 which receives air under pressure.

The velocity of the air jet which rises in the lower conical portionof each chamber decreases as the cross-sec-f tional area increases, whereby the heaviest particles tend to float or whirl in the said portion in a per se known manner without being entrained by the. air stream. In the upper conical portion the air introduction through the additional tangential air inlets 10' and 10" generates a rotational movement of the air about the vertical axis of the chamber. The heaviest particles which have reached this zone are therefore thrown by centrifugal force against the conicalvwall of the said upper portion and owing to theobliquity of this wall, they tend to roll downwardly towards the intermediate cylindrical portion of the chamber. The lightest particles are carried'away by the outgoing air. The upper chamber 29 being of larger diameter, this selective effect due ,to centrifugal force is more marked and therefore the centrifugal separator 7 only receives dry or practically dry particles.

It is to be noted that the fresh hot air is injected tangentially into each chamber somewhat above the horizontal plane of symmetry of the latter, ile. in a zone where the air issuing from the lower axial inlet of the chamber has already absorbed a noticeable amount'of moisture from the particles. This tangentialinjection therefore enhances the drying power of the airin which'the particles are in suspension.

The balls 27. are lifted by the air issuing from the lower inlet of chamber 29. and they vibrate in the lower conical portion of the chamber where they strike the particles in,

suspension. They thus form a kind of vibrating screen 4 which preventsvthe heaviest particles from rising directly into the upper portion of the chamber 29 without previously whirling in the lower portion thereof. Owing to their weight these balls remain at a level where. the ascending velocity of the air is-such that they are not liable to be entrained into the exhaust conduit 6.

The air withdrawn by the exhaustblowerj 8 is taken from the outlet of the drying conduit 6." In other words the air forced. through the inner nozzle 31 is re-cycled from the outlet of the drier into the inlet thereof while at the same time inducing hot and dry air from generator 2 into the drying chambers.

It will be appreciated that the embodiment of FIG. 3 could comprise a mainblower as in the case of FIG. 1, also that the additional drying air pipe 30, the main role of which is to supply air under pressure to the inner nozzle 31 in order to increase the'velocity of the air jet through chambers 28 and 29, could be dispensed with, more particularly when such a main blower is provided between the main nozzle 4 and the heat generator 2.

I claim:

1. A pneumatic drier comprising means to form a stream of relatively hot and dry. drying gas; means to introduce into said stream a divided material in the form of substantially discrete. particles; at least one substantially vertical bi-conical drying chamber having a lower P upwardly flaring conical portion and an upper downwardly flaring [conical portion substantially symmetrical V ,with said lower conical portion with respect to a horizontal plane, said chamber further having an upper end and a lower end; outlet means connected with the upper end of said chamber;.inlet means opening axially into the lower end of said chamber, said inlet means receiving said stream with said divided material introduced there.- into to produce in said chamber an ascending jet of drying gas with said particles in suspension therein; balls disposed in said chamber to be lifted'in the lower conical portion thereof by said ascending jet of drying gas; a transverse grid in the lower end of said chamber to prevent said balls'frorn falling therethrough; an additional gas inlet opening tangentially into said chamber, substantially midway'of the height thereof; means to supply to said additional gas inlet substantially hot and dry drying gas substantially free from suspended particles of divided material; and means to separate the dried particles from the gas issuing from said outlet means.

2. A pneumatic drier comprising means to form a stream of relatively hot and dry drying gas; means to introduce into said stream a divided material in the form of substantially discrete particles; a first substantially vertical bi-conical drying chamber having a lower upwardly flaring conical portion and an upper downwardly flaring conical portion substantially symmetrical with said lower conical portion with respect to a horizontal plane, said first chamber further having anupper end and a lower end; first outlet means connected with the upper end of said first chamber; first inlet means opening axially into the lower end of said first chamben'said first inlet means receiving said stream with said divided material introduced thereinto to produce in said chamber an ascending jet of drying gas with said particlesinsuspension therein; a first additional gas inlet opening tangentially into said first chamber, substantially midway of the height thereof; means to supply to said first additional gas inlet substantially hot and dry gas substantially free from suspended particles of divided material; a second substantially biconical drying chamber of substantially larger maximum diameter than said first drying chamber and disposed substantially axially above same, said second chamber also having a lower upwardly flaring conicalportion and an upper downwardly, flaring conical portion substantially symmetrical'with said upper conical portion With respect to a horizontal plane,said second chamber further having an upper end and a lower end; second outlet means connected with the upper end of said second chamber; second inlet means opening axially into the lower end of said second chamber and connected with said first outlet means to receive therefrom drying gas with particles of divided material in suspension therein and to form in said second chamber an ascending jet of gas and suspended particles; a second additional gas inlet opening tangentially into said second chamber substantially midway of the height thereof; means to supply to said second additional gas inlet substantially hot and dry drying gas substantially free from suspended particles of divided material; and means to separate the dried particles from the gas issuing from said second outlet means.

References Cited by the Examiner UNITED STATES PATENTS Peebles 34-57 X Winter 34-57 X Manning et a1. 34-57 X Stephanofi 34-57 X Shaw 34-57 X Rycke 34-57 X Doleman et al. 34-95 Mark 34-57 X NORMAN YUDKOFF, Primary Examiner. 

1. A PNEUMATIC DRIER COMPRISING MEANS TO FORM A STREAM OF RELATIVELY HOT AND DRY DRYING GAS; MEANS TO INTRODUCE INTO SAID STREAM A DIVIDED MATERIAL IN THE FORM OF SUBSTANTIALLY DISCRETE PARTICLES; AT LEAST ONE SUBSTANTIALLY VERTICAL BI-CONICAL DRYING CHAMBER HAVING A LOWER UPWARDLY FLARING CONICAL PORTION AND AN UPPER DOWNWARDLY FLARING CONICAL PORTION SUBSTANTAILLY SYMMETRICAL WITH SAID LOWER CONICAL PORTION WITH RESPECT TO A HORIZONTAL PLANE, SAID CHAMBER FURTHER HAVING AN UPPER END AND A LOWER END; OUTLET MEANS CONNECTED WITH THE UPPER END OF SAID CHAMBER; INLET MEANS OPENING AXIALLY INTO THE LOWER END OF SAID CHAMBER, SAID INLET MEANS RECEIVING SAID STREAM WITH SAID DIVIDED MATERIAL INTRODUCED THEREINTO TO PRODUCE IN SAID CHAMBER AN ASCENDING JET OF DRYING GAS WITH SAID PARTICLES IN SUSPENSION THEREIN; BALLS DISPOSED IN SAID CHAMBER TO BE LIFTED IN THE LOWER CONICAL PORTION THEREOF BY SAID ASCENDING JET OF DRYING GAS; A TRANSVERE GRID IN THE LOWER END OF SAID CHAMBER TO PREVENT SAID BALLS FROM FALLING THERETHROUGH; AN ADDITIONAL GAS INLET OPENING TANGENTIALLY INTO SAID CHAMBER, SUBSTANTIALLY MIDWAY OF THE HEIGHT THEREOF; MEANS TO SUPPLY TO SAID ADDITIONAL GAS INLET SUBSTANTIALLY HOT AND DRY DRYING GAS SUBSTANTIALLY FREE FROM SUSPENDED PARTICLES OF DIVIDED MATERIAL; AND MEANS TO SEPARATE THE DRIED PARTICLES FROM THE GAS ISSUING FROM SAID OUTLET MEANS. 